Method for manufacturing magnetic material of high permeability in sheet form



Sept. 19, 1939. e. WASSERMANN METHOD FOR MANUFACTURING MAGNETIC MATERIAL OF HIGH PERMEABILITY IN SHEET FORM Filed March 6, 1937 1 r presents a d agr s ra tion and vice versa, and these crystal positions of. Crystal po i are, therefore, always destroyed during the next Fig. 2 diagrammatically represents test results, rolling operation. and The manufacture of materials in sheet form 3 ram i lly r p n s an arrangeand particularly in bands or tapes by the remeht for transverse rollihgpeated cross-rolling process as heretofore prac- The structure of the material resulting from ticed presents, however, certain technical diiiithe rolling of metals with body centered atom crimes, In the normal longitudinal rolling lattices is Simple a co p d to t e face cen process, the material retains its width quite well I ed etals- AS wil be See om t e po so that also the length of the rolls may remain tion a in 1 the crystals lie n 'I t Q the-same during the rolling process. However, in which the diagonal d of one of the surfaces of when cross-rolling the material, the length and a cube is located in parallel relation to the di-' the width of the sheet increase to the same exrection of rolling and this cube surface is in the tent. 'The material must, therefore, be often-cut, ideal case parallel to the-plane of the rolled which may be avoided for thin sheet iron to a sheet iron. However, this ideal position 'cancertain extent only by the use of very long rolls, not be practically attained 'for all crystals. The This disadvantage is removed by the method accompanying dispersion (which is always presaccording to the invention which requires only ent also in the best structures) consists in a one change of the direction of rolling. The deviation Which is p oduced by rotation of the method consists in first cold rolling the ferrocrystals approximately 1-4.0 about ,the' face -di-, magnetic specimen down to about one-eighth to agonald lying in the direction of rolling. Posione-tenth of its original thickness and in subsetions b and cshow schematically two such posiquently cold rolling it in a directionwhich is distions of dispersion. The position ,for.the diplaced 90 with respect to the first direction-of rection of the easiest m etization-name y, rolling, down to about half the thickness at-- the direction along the edge of the cube, which tained after the first rolling operation, which in the illustrated ideal position a is located in thickness is the final, desired one. c the plane of-the sheet iron at an angle or 45 The tests carried'out in-this connectionhad the to the direction of rolling and to the transverse following result which is diagrammatically repredirection, that is to say, is quite favorable for sented in Fig. 2; In this figure the percentage magnetic purposesis changed and the cube is of reduction in thickness by the first rollingrotated by the dispersion out of the plane of the process is plotted against the percentage of sheet iron into positions whose geometric locus is reduction in thickness by the second rolling a cone about. the direction of rolling with a 'process in a direction at rightangles to the I opening angle of approximately 45. direction of the first process. The rolling ratios The conditions for a magnetically favorable represented by; the encircled points showed in the 40 behavior of this structure are only fulfilled if it tests that the crystal orientation produced by the is possibleto reduce thedispersion sothat the first rolling direction was preponderant, the edges and the planes of the cube lie to a great ratios represented by the heavy solid points extent only in the plane of the sheet iron. A showed the orientation of-the second rolling diknown process .shows'a method for solving this rection to be preponderant, and the ratios repreproblem which consists in rolling the sheet iron sented by the crossed points showed that the a number of times alternately in two directions orientation effects of both rolling directions. were at right angles to one another and to thereby equal. For further. elucidating the way of regisvery gradually roll the material down to the detering used -in'the diagram, an example may be sired thickness. In Fig. 1, for instance, one of. taken .in view. Point A in Fig. -2 represents a Patented Sept. 19, 1939 METHOD FOR MANUFACTURING MAGNETIC MATERIAL OF HIGH PERMEABILITY IN SHEET FORM.

Giinter Wassermann, Bcrlin-Wilmersdorf, Germany, asslgnor to Siemens & Halske, Aktiengesellschaft, Siemcnsstadt, near Berlin, Germany, a corporation of Germany Application March 6, 1937, Serial No. 129,362

Germany March 6, 1936 '3 Claims. 01. 148-12) y inv n i n relates to a method for manupondering number are located in the ideal positu n m n tic material of h h p m ity tion, for the positions of dispersion characterin sheet form. It is illustrated in the accomistic of one rolling direction arenot suitable for D ny r w n in wh the structure characteristic of the other directhese two directions (longitudinal rolling) is indicated by an arrow marked LR, and the other direction (transversal rolling) by an arrow marked TR. The cross-rolling operation leadsto a structure in which the crystals in a presheet iron treated as follows. The sheet was first cold rolled with a rolling degree 'of 82% (see abscissa), that is, reduced to a thickness of a little more than /5 of the' original thickness. "Then a crosswise rolling was applied. resulting in a further reduction of 50% (see ordinate).

. The fact that dot A is of heavy solid type also shows that after these treatments the effect of the second rolling was preponderant as manitested by a crystal orientation corresponding to the direction of the second cold rolling operation.

, The range of percentage of reduction employed in the first cold rolling operation was selected between 82-95% with a sheet iron thickness between 1.2 and 0.3 mm. after the first rolling.

It is not convenient to employ sheet iron with a lower degree of reduction for'the first rolling operation, since the structure in this material is still far from being properly developed. The tests showed that during the second rolling operation, 'in a direction displaced from the first rolling direction, the dispersion decreases about the first direction of rolling. The structure becomes symmetrical with respect to both directions and, on further rolling in the second direction, finally the dispersion increases considerably about the seconddirection or rolling, so that a normal structure of the rolled material is again attained.

When employing reductions below 36% for the second direction of rolling the points I, I, I show that the orientation resulting from the first rolling was always predominant. In the case of sheet iron prerolled to a reduction by 90 to a symmetrical structure was attained when the material obtained from the rolling in the first direction was reduced by 50-55% in the second direction (points 2, 2, 2) and in the case of sheet iron prerolled to a reduction by 82% symmetry was attained already by reducing it 40% during rolling in the second direction. With higher degrees of reduction in the second direction, the structure resulting from this direction of rolling is in most cases predominant.

This result means that a material rolled in sheet form in one direction, for instance from 6 mm. to 0.6 mm. need only be additionally rolled to 0.3 mm. transversely to the first direction of rolling and to its final gauge in order to attain a symmetrical structure. Consequently, in the first direction oi rolling, the material must be lengthened to about ten times its original length, whereas in the second direction of rolling only to two times the length, and thus the cross-rolling process is considerably simplified.

The method according to the invention may also be applied to the manuiacture of steel tape for armoring purposes or the like. The first rolling operation is efiected in this casein the normal manner heretofore practiced. For. the second rolling operation, rolling mills as shown in Fig. 3 are employed which permit a lateral passage of the tape through the housings in which the bearings of the top and bottom rolls are spaced from one another. The tape is fed in parallel relation to the axes of the rolls and cross-rolled. After one or more passages through the rolls the tape is advanced an amount equal to the length of the roll and is then again cross-rolled etc.

To attain a high permeability and low losses the material with body centered crystal grids must be annealed after the rolling operation.

However, during this annealing treatment, the uniform structure attained by the rolling operation should be largely maintained. In order that the crystals formed during the recrystallization have as far as possible the orientation of the deiormed crystals it is necessary that the annealing being easiily deformed and, on the other hand,

comparatively high values of permeability may be attained.

I claim as my invention:

1. A method of manufacturing magnetic materials of high permeability in sheet form from materials with body-centered cubic atom lattices consisting in first cold rolling the specimen to reduce it to about one-eighth to one-tenth of its original thickness, in subsequently cold rolling it in a direction displaced 90 with respect to the first rolling direction to reduce it to about half the thickness attained after the first rolling, and representing the final thickness, and in then heat treating the specimen at temperatures lying between 600 and 1000' degrees centigrade.

2. A method of manufacturing magnetic materials of high permeability in tape form from materials with body-centered cubic atom lattices consisting in longitudinally cold-rolling the material to reduce it to one-eighth to one-tenth of its original thickness, in subsequently rolling it in a direction displaced 90 with respect to the first direction of rolling to reduce it to approximately one-half of the thickness attained by the longitudinal rolling and in a rolling mill through which the tape is fed in parallel relation to the axes of the rolls and cross-rolled in several passes to the aforesaid thickness as the final form, and in subsequently heat treating the finally rolled tape at temperatures lying between 600 and 1000 degrees centigrade.

3. A method 0! manufacturing magnetic materials of high permeability in sheet form from iron-silicon alloys'containing up to 5% silicon consisting in cold 'rollingthe material to reduce it to one-eighth to one-tenth of its original thickness, in subsequently rolling it in a direction displaced 90 with respect to the first direction of rolling to reduce it to approximately one-half of 

